Oil based compositions and method for temporarily sealing subterranean zones

ABSTRACT

The present invention provides oil based compositions and methods of using the compositions for temporarily sealing subterranean zones. The compositions are basically comprised of oil, a hydratable polymer, an organophilic clay, a water-swellable clay, and an acid soluble material such as calcium carbonate. These compositions will form a viscous gel when contacted with water. The gelled mass may then be dissolved with an acidic fluid, such as 15% hydrochloric acid.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a Divisional of application Ser. No.09/884,683 filed on Jun. 19, 2001, now pending.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to improved oil based compositionsfor temporarily sealing subterranean zones and methods of utilizing thecompositions.

[0003] In the drilling of oil and gas wells using the rotary drillingmethod, drilling fluid is circulated through the drill string and drillbit and then back to the surface by way of the well bore being drilled.The drilling fluid maintains hydrostatic pressure on the subterraneanzones through which the well bore is drilled and circulates cuttings outof the well bore. During such drilling, subterranean vugs, fractures,and other thief zones are often encountered whereby the drilling fluidcirculation is lost, and drilling operations must be terminated whileremedial steps are taken. Also, when a subterranean zone is penetratedcontaining fluids under pressure which exceeds the hydrostatic pressureexerted on the zone by the drilling fluid, formation fluid crossbowsand/or underground blow-outs can and often do occur. As a result,drilling fluid circulation is often lost which requires the terminationof the drilling and the implementation of remedial procedures which areoften of long duration and high cost.

[0004] U.S. Pat. No. 6,060,343 issued May 9, 2000 having inventorsRonald E. Sweatman and James F. Heathman and issued to HalliburtonEnergy Services, Inc. describes oil based compositions and methods ofusing the compositions for sealing subterranean zones. The compositionsare basically comprised of oil, a hydratable polymer, an organophilicclay, and a water-swellable clay. These compositions and methods developultra high viscosity in a few seconds or minutes, solving many problemsassociated with prior art methods and compositions, and have been highlysuccessful for sealing subterranean zones. The specification of U.S.Pat. No. 6,060,343 is incorporated herein by reference in its entirety.

[0005] It is sometimes desirable, however, to temporarily seal asubterranean zone. Thus, there is a need for improved compositions andmethods for sealing subterranean zones having the benefits andadvantages of the compositions disclosed in U.S. Pat. No. 6,060,343 andthat would have the additional benefit of temporarily sealingsubterranean zones. After having been sealed for the desired wellworkover activity, it would be desirable to be able to easily andquickly reopen the subterranean zones. It would still be important,however, that such a seal not be easily washed out or removed until itis desired to remove the plug and reopen the zone.

SUMMARY OF THE INVENTION

[0006] Improved oil based compositions for temporarily sealingsubterranean zones and methods of using the compositions are providedand meet the need described above. The compositions are basicallycomprised of oil, a hydratable polymer, an organophilic clay, awater-swellable clay, and an acid soluble material. These compositionswill form a viscous gel when contacted with water. The gelled mass maythen be dissolved with an acidic fluid, such as 15% hydrochloric acid inwater. Thus, the temporary seal is not easily washed out or removeduntil it is desired to remove the plug and reopen the zone Thecompositions can also include cross-linking agents, dispersing agents,cement, fillers and the like, provided that any such other materials donot adversely affect the desired functions of the compositions accordingto the invention.

[0007] When the temporary sealing compositions of this invention contactwater in the well bore, the hydratable polymer reacts with the water,whereby it is hydrated and forms a highly-viscous gel and thewater-swellable clay swells, whereby an ultra high viscosity mass isformed. The organophilic clay adds viscosity to the sealing compositionwhen it is formed, i.e., it reacts with the oil carrier fluid andprevents the polymer and water-swellable clay from settling out of thecomposition.

[0008] When the highly viscous gelled mass is contacted or washed withan acidic fluid, such as 15% hydrochloric acid, the acid solublematerial dissolves, which substantially reduces the viscosity of thegelled mass. The reduced viscosity of the gelled mass allows it to bewashed away from the subterranean zone and reopen the zone.

[0009] A composition for temporarily sealing a subterranean zone toprevent the uncontrolled flow of fluids into or from the zone preferablycomprises: first component comprising oil; the balance of the temporarysealing composition comprising a second component and a third component,wherein the second component comprises: a hydratable polymer, anorganophilic clay, and a water-swellable clay; and the third componentcomprises an inorganic material that is readily acid soluble butsubstantially insoluble in neutral or basic water; wherein the secondcomponent is present in an amount in the range of from about 10% toabout 90% by weight of the balance of the temporary sealing composition,and wherein the third component is present in an amount in the range offrom about 10% to about 90% by weight of the balance of the temporarysealing composition.

[0010] Preferably, the second component comprises: a hydratable polymerpresent in an amount in the range of from about 4.4% to about 14.6% byweight of the second component; an organophilic clay present in anamount in the range of from about 0.4% to about 1.6% by weight of thesecond component; and a water-swellable clay present in an amount in therange of from about 84% to about 95% by weight of the second component.

[0011] The methods of the invention comprise the steps of preparing atemporary sealing composition of this invention, introducing it into thesubterranean zone to be sealed, and subsequently removing the temporarysealing composition by washing with an acidic solution.

[0012] It is, therefore, a general object of the present invention toprovide improved oil based compositions and methods for temporarilysealing subterranean zones and methods. Other and further objects,features, and advantages of the present invention will be readilyapparent to those skilled in the art upon a reading of the descriptionof preferred embodiments which follows.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0013] The present invention provides improved oil based compositionsfor temporarily sealing subterranean zones and terminating the loss ofdrilling fluid, crossflows, and/or underground blow-outs. When atemporary sealing composition of this invention contacts water in thewell bore, it immediately forms a resilient sealing mass having ultrahigh viscosity. As the sealing mass is displaced through the well bore,it enters and seals thief zones such as vugs and fractures through whichfluid is lost. A flexible seal is obtained by a combination of extrusionpressure and friction pressure. When the highly-viscous gelled mass iscontacted or washed with an acidic fluid, such as 15% hydrochloric acid,the acid soluble material dissolves, which substantially reduces theviscosity of the gelled mass. The reduced viscosity of the gelled massallows it to be washed away from the subterranean zone and reopen thezone.

[0014] The temporary sealing compositions of this invention are selfdiverting and plug multiple weak zones in a single well treatment. Whena well contains a crossflow or underground blow-out, the high viscositysealing compositions plug all the lower pressure weak zones penetratedby the well bore, and, as the pressure in the well bore is increased,the crossflow or blow-out zone is plugged. The resultant sealed wellbore achieved by the temporary sealing compositions of this inventioncan hold higher drill-ahead drilling fluid weights and produce a wedgingeffect in plugged fractures that increases the integrity of the entireformation or zone.

[0015] The portion of a temporary sealing composition left in the wellbore after sealing one or more zones therein remains movable to divertto other zones above or below the sealed zones. The sealing mass is notreadily diluted or washed away by crossflows as are most prior artcompositions.

[0016] The temporary sealing compositions of the present invention arebasically comprised of oil, a hydratable polymer, an organophilic clay,a water-swellable clay, and an acid soluble material. The hydratablepolymer reacts with water in the well bore and is immediately hydrated,whereby a highly-viscous gel is formed. The water-swellable clayimmediately swells in the presence of water and, together with theviscous gel, forms a highly-viscous sealing mass. The organophilic clayreacts with the oil carrier fluid to add viscosity to the composition sothat the polymer and clay do not settle out of the oil prior to reactingwith water in the well bore. The acid soluble material is suspended inthe viscous sealing mass.

[0017] A composition for temporarily sealing a subterranean zone toprevent the uncontrolled flow of fluids into or from the zone preferablycomprises: a first component comprising oil, the balance of thetemporary sealing composition comprising a second component and a thirdcomponent, wherein the second component comprises: a hydratable polymerpresent in an amount in the range of from about 4.4% to about 14.6% byweight of the second component; an organophilic clay present in anamount in the range of from about 0.4% to about 1.6% by weight of thesecond component; and a water-swellable clay present in an amount in therange of from about 84% to about 95% by weight of the second component;and the third component comprises an inorganic material that is readilyacid soluble but substantially insoluble in neutral or basic water;wherein the second component is present in an amount in the range offrom about 10% to about 90% by weight of the balance of the temporarysealing composition, and wherein the third component is present in anamount in the range of from about 10% to about 90% by weight of thebalance of the temporary sealing composition.

[0018] The oil utilized in accordance with this invention can be any oilwhich does not adversely react with other components of the sealingcompositions and reacts with organophilic clays to bring about anincrease in the viscosity of the compositions prior to contacting water.The term “oil” is used herein to mean non-aqueous liquids including, forexample, diesel oil, mineral oils, kerosene, vegetable oils, syntheticoils, esters, olefins, and the like. Of these, diesel oil is preferred.The oil used is generally included in the sealing compositions of thisinvention in an amount in the range of from about 32% to about 62% byweight of the temporary sealing compositions. When diesel oil is used,it is preferably included in the temporary sealing compositions in anamount in the range of from about 43% to about 53% of the temporarysealing compositions.

[0019] A variety of well known hydratable polymers can be utilized inaccordance with the present invention. Generally, they includehydratable polymers which contain one or more of the functional groupssuch as hydroxyl, cis-hydroxyl, carboxyl, sulfate, sulfonate, amino oramide. Particularly useful such polymers are polysaccharides andderivatives thereof which contain one or more of the monosaccharideunits galactose, mannose, glucoside, glucose, xylose, arabinose,fructose, glucuronic acid, or pyranosyl sulfate. Natural hydratablepolymers containing the foregoing functional groups and units includeguar gum and derivatives thereof, locust bean gum, tara, konjak,tamarind, starch, cellulose and derivatives thereof, karaya, xanthan,tragacanth and carrageenan. Hydratable synthetic polymers and copolymerswhich contain the above mentioned functional groups and which have beenutilized heretofore include polyacrylate, polymethacrylate,polyacrylamide, maleic anhydride, methylvinyl ether polymers, polyvinylalcohol, and polyvinylpyrrolidone.

[0020] Preferred hydratable polymers for use in accordance with thisinvention which yield high viscosities upon hydration include one ormore of guar gum and guar derivatives such as hydroxypropylguar andcarboxymethylguar, cellulose derivatives such as hydroxyethylcellulosecarboxymethylcellulose and carboxymethylhydroxyethylcellulose, locustbean gum, carrageenan gum, and xanthan gum. Of these, the most preferredis hydroxyethylcellulose. The hydratable polymer or polymers used areincluded in the second component in an amount in the range of from about4.4% to about 14.6% by weight of the second component, more preferablyfrom about 6% to about 12% by weight of the second component.

[0021] The viscosities of the polymers when hydrated in water can beincreased by combining crosslinking agents with the polymer solutions.Examples of crosslinking agents which can be utilized are multivalentmetal salts or compounds which are capable of releasing the metal ionsin an aqueous solution. Examples of such multivalent metal ions arechromium, zirconium, antimony, titanium, iron (ferrous or ferric), zinc,or aluminum. When used, a crosslinking agent as described above isincluded in the second component in an amount in the range of from about0.05% to about 9% by weight of the second component, more preferablyfrom about 0.05% to about 3% by weight of the second component.

[0022] While a variety of organophilic clays can be utilized, an alkylquaternary ammonium bentonite clay is preferred. A particularly suitablealkyl quaternary ammonium bentonite clay for use in accordance with thepresent invention is commercially available from Southern Clay Products,Inc. of Gonzales, Tex. under the tradename “CLAYTONE-II.TM.” Theorganophilic clay is generally present in the compositions of thisinvention in an amount in the range of from about 0.4% to about 1.6% byweight of the second component, more preferably from about 0.6% to about1.3%.

[0023] The water-swellable clay can be one or more clays selected frommontmorillonite, attapulgite, Fuller's earth, bentonite, and the like.Of these, bentonite is preferred. The water-swellable clay is present inthe sealing compositions in an amount in the range of from about 84% toabout 95% by weight of the second component, more preferably about 90%.

[0024] The third component of the temporary sealing compositions is anacid soluble material. As used herein, an acid soluble material is amaterial that is readily soluble in acidic water but insoluble in basicor neutral pH water. Preferably, the acid soluble material is no morethan about 1% by weight soluble in de-ionized water when tested at a pHof about 7, a temperature of about 212° F., and a pressure of about 1atmosphere. As used herein, readily soluble means that at least 1% byweight of the material dissolves in 100 grams of water within less thanone minute with stirring. Although there is not a bright line, thedifference between acid solubility and solubility in water having aneutral or basic pH is critical to the function of the temporary sealingcompositions and the methods of using them for temporarily sealingsubterranean zones.

[0025] To facilitate carrying or suspending the acid soluble material inthe oil based component and to facilitate dissolving the acid solublematerial in an acidic solution, the acid soluble material is preferablyless than about 40 mesh. More preferably, the acid soluble material isabout 200 mesh.

[0026] In addition to acid solubility, another important criteria forselecting the acid soluble material is the cost of the material.Preferably, readily available, low-cost materials are used.

[0027] Preferably, the acid soluble material is an inorganic carbonate,and more preferably the inorganic acid material is selected from thegroup consisting of calcium carbonate, magnesium carbonate, bariumcarbonate, and iron (II) carbonate, or any combination thereof. Mostpreferably, the acid soluble material is calcium carbonate.

[0028] In some temporary sealing compositions according to theinvention, the second component can be present in an amount in the rangeof from about 10% to about 90% by weight of the balance of the temporarysealing composition, and the third component can be present in an amountin the range of from about 10% to about 90% by weight of the balance ofthe temporary sealing composition. More preferably, the second componentis present in an amount in the range of from about 30% to about 70% byweight of the balance of the temporary sealing composition, and thethird component is present in an amount in the range of from about 30%to about 70% by weight of the balance of temporary sealing composition.Most applications are expected to work well wherein the second componentis present in an amount of about 50% by weight of the balance of thetemporary sealing composition, and the third component is present in anamount of about 50% by weight of the balance of the temporary sealingcomposition.

[0029] In order to facilitate the dispersal of the solid materials,i.e., the hydratable polymer, the organophilic clay, the water-swellableclay, and the acid soluble material in the oil carrier fluid used, aneffective amount of a dispersing agent can be included in the temporarysealing compositions. Various dispersing surfactants can be utilizedincluding lecithin, aminododecylbenzene sulfonate, aryl alkyl sodiumsulfonate, imodazolin, and others. Of these, lecithin is preferred.

[0030] Inert fillers can be included in the temporary sealingcompositions to increase the downhole yield of the compositions and/orprovide additional hardness to the compositions. Examples of suchfillers are silica flour, silica fume, pozzolans, and the like.Hardenable hydraulic materials such as Portland cement and slag can alsobe added to the sealing compositions to alter and/or enhance theproperties of the sealing masses formed when the sealing compositionscontact water in a well bore.

[0031] The temporary sealing compositions can also be foamed withnitrogen or other suitable gas in the presence of a foaming agent forreducing the densities of the compositions, preventing fluid loss andaiding in the diversion of the compositions into zones to be sealed. Asuitable foaming agent which can be used is a fluorocarbon surfactant.

[0032] Other additives which are well known to those skilled in the artcan also be included in the compositions.

[0033] The temporary sealing compositions of this invention can beprepared in accordance with any of the well known mixing techniques. Ina preferred method, the oil used is second introduced into a blender.The dispersant and other liquid additives are then added followed by thehydratable polymer, organophilic clay, water-swellable clay, acidsoluble material, and other dry solids. The mixture is agitated for asufficient period of time to mix the components and form a pumpableslurry. If convenient, the second component comprising oil,hydroxyelthylcellulose, alkyl quaternary ammonium bentonite clay, andwater-swellable bentonite clay is mixed second, which can be used eitheras a permanent sealing composition as disclosed in U.S. Pat. No.6,060,343 or as the second component of a temporary scaling compositionas disclosed herein.

[0034] The methods of this invention for temporarily sealing asubterranean zone to prevent the uncontrolled flow of fluids into orfrom the zone basically comprise the steps of preparing a subterraneanzone temporary sealing composition of this invention comprising oil, ahydratable polymer, an organophilic clay, a water-swellable clay, and anacid soluble material, and then introducing the temporary sealingcomposition into the zone to be sealed. Generally, the temporary sealingcomposition is prepared in a mixing apparatus at the surface and thenpumped down the well bore into the zone to be sealed at a high pressure,whereby the sealing mass formed in the well bore is squeezed intofractures and vugs therein. A fluid pressure above the fracture gradientof the zone can also be used in some applications to fracture the zonebeing sealed and force the sealing composition into the fractures,thereby increasing the overall strength of the zone. As mentioned, thetemporary sealing composition enters the weakest portions of the zonesecond followed by other portions including those where fluids crossflowthrough the well bore or blow-out into the well bore. The temporarysealing composition stops drilling fluid losses and allows high drillingfluid densities to be utilized when needed while drilling ahead. Oncethe temporary sealing composition has been placed, it increases thefracture gradient to a higher value that can eliminate the need forintermediate casing, drilling liners, and the like. Because thetemporary sealing composition readily diverts to other weak zones in thewell bore, the integrity of the entire well bore is improved by thetemporary sealing composition.

[0035] In order to further illustrate the temporary sealing compositionsand methods of the present invention, the following examples are given.In general, an oil based temporary sealing composition of the presentinvention was prepared in the laboratory. A portion of the temporarysealing composition was added to an equal portion of a water baseddrilling fluid. Within about 10 seconds a solid high-viscosity mass wasformed which had a moldable consistency. The high viscosity mass wasthen readily dissolved within about one minute by washing with an acidicfluid, such as 15 wt% hydrochloric acid in de-ionized water.

EXAMPLES

[0036] More particularly, the following illustrative examples areprovided:

[0037] A first component for use in preparing the illustrative examplesof a temporary sealing composition was No. 2 diesel.

[0038] A second component for use in preparing the illustrative examplesof a temporary sealing composition included the following: 8.4 wt%hydroxyethylcellulose; 0.9 wt% organophilic clay; 90 wt% bentonite clay;and 0.7 wt% zirconium oxychloride.

[0039] A third component for use in preparing the illustrative examplesof a temporary sealing composition was 200 mesh calcium carbonate.

[0040] The first component, No. 2 diesel, comprised 50% by weight of thefollowing illustrative examples of the temporary sealing compositions.The balance of the illustrative examples of the temporary sealingcompositions were either 50% by weight of the second component and 50%by weight of the third component or 30% by weight of the secondcomponent and 70% by weight of the third component.

[0041] Normally, slurry containing the first, second, and thirdcomponents is prepared with a batch mixer, which helps ensure uniformityand fluid quality, but it can also been mixed on-the-fly. The firstcomponent, i.e., the oil, is normally first placed in a batch mixer. Thesecond and third components, being dry material, are then added. Thesecond and third components can be mixed together before adding to theoil or added separately to the oil. To avoid sedimentation after mixing,stir or circulate the mixture at a low rate until the material ispumped.

[0042] The temporary sealing compositions were tested for gelation usingthe representative 9.5 lb/gal muds shown in Table 1. TABLE 1 ComponentsMud #1 Mud #2 Mud #3 Mud #4 Freshwater, bbl 0.94 0.94 0.94 0.93 Wyomingbentonite clay 15 8 20 25 (Montmorillonite), lb Oxidized lignite, lb — —4 8 Ferrochrome lignosulfonate, lb — — — 2 Acrylic acid grafted ontocalcium — — 4 — lignosulfonate, lb Caustic Soda, lb 0.1 0.2 1.5 2 Lime,lb — — 4 0.3 Polyanionic cellulose; actually, — 0.55 — carboxymethylcellulose, lb Acrylamide/acrylic acid copolymer — 0.5 — — emulsion, lbPotato Starch, lb 4 5 4 — Brazan-D Plus, lb — 0.2 0.55 0.4 Barite; sameas Barium Sulfate, lb 36.8 42.45 36.8 28.74 Rev Dust, lb 18.2 18.2 18.218.2

[0043] The gelation tests were conducted by mixing equal volumes of thetemporary sealing composition with the mud. Tables 2-4 illustrate thegelation results when these illustrative examples of the temporarysealing compositions were tested at 190° F. and ambient temperature withMud Nos. 1-4. TABLE 2 190° F. Gelation Test Results Diesel Oil Carrierwith balance of 50% Second Component and 50% Third Component Mud Resultsof Mixing with Plug Material #1 Immediate gelation #2 Immediate gelation#3 Immediate gelation #4 Immediate gelation

[0044] TABLE 3 Ambient Temperature Gelation Test Results Diesel OilCarrier with 50% Second Component and 50% Third Component Drilling FluidResults of Mixing with Plug Material #1 Immediate gelation #2 Immediategelation #3 Immediate gelation #4 Immediate gelation

[0045] TABLE 4 Ambient Temperature Gelation Test Results Diesel OilCarrier with 30% Second Component and 70% Third Component Drilling FluidResults of Mixing with Plug Material #3 Immediate gelation #4 ImmediateGelation

[0046] Samples of the gelled fluids, approximately 20 cc in volume, wereplace in 1 liter of 15% hydrochloric acid. In all cases, the calciumcarbonate in the gelled material dissolved, and the remaining materialdispersed in the acidic solution.

[0047] Thus, the present invention is well adapted to carry out theobjects and attain the benefits and advantages mentioned as well asthose which are inherent therein. While numerous changes to thecompositions and methods can be made by those skilled in the art, suchchanges are encompassed within the spirit of this invention as definedby the appended claims.

What is claimed is:
 1. A composition for temporarily sealing asubterranean zone to prevent the uncontrolled flow of fluids into orfrom the zone comprising: a first component comprising oil, wherein thebalance of the composition comprises: a second component present in anamount in the range of from about 10% to about 90% by weight of thebalance of the composition comprising a hydratable polymer, anorganophilic clay, and a water-swellable clay, and a third componentpresent in an amount in the range of from about 10% to about 90% byweight of the balance of the composition comprising an inorganicmaterial that is readily acid soluble but substantially insoluble inneutral or basic water.
 2. The composition of claim 1 wherein the thirdcomponent is no more than about 1% by weight soluble in de-ionized waterwhen tested at a pH of about 7, a temperature of about 212° F., and apressure of about 1 atmosphere.
 3. The composition of claim 1 whereinthe oil is present in an amount in the range of from about 32% to about62% by weight of the composition.
 4. The composition of claim 1 whereinthe hydratable polymer is present in an amount in the range of fromabout 4.4% to about 14.6% by weight of the second component.
 5. Thecomposition of claim 1 wherein the organophilic clay is present in anamount in the range of from about 0.4% to about 1.6% by weight of thesecond component.
 6. The composition of claim 1 wherein thewater-swellable clay is present in an amount in the range of from about84% to about 95% by weight of the second component.
 7. The compositionof claim 1 wherein the third component is selected from the groupconsisting of calcium carbonate, magnesium carbonate, barium carbonate,and iron (II) carbonate.
 8. The composition of claim 1 wherein the thirdcomponent is calcium carbonate.
 9. The composition of claim 1 whereinthe third component has a mesh size of up to about
 40. 10. Thecomposition of claim 1 wherein the third component has a mesh size ofabout
 200. 11. The composition of claim 1 wherein the second componentis present in an amount in the range of from about 30% to about 70% byweight of the balance of the composition, and wherein the thirdcomponent is present in an amount in the range of from about 30% toabout 70% by weight of the balance of the composition.
 12. Thecomposition of claim 1 wherein the second component is present in anamount of about 50% by weight of the balance of the composition, andwherein the third component is present in an amount of about 50% byweight of the balance of the composition.
 13. The composition of claim 1wherein the oil is selected from the group consisting of diesel oil,mineral oils, kerosene, vegetable oils and synthetic oils, esters, andolefins.
 14. The composition of claim 1 wherein the oil is diesel oil.15. The composition of claim 1 wherein the hydratable polymer isselected from the group consisting of guar gum, hydroxypropylguar,carboxymethylguar, hydroxyethylcellulose, carboxymethylcellulose,carboxymethylhydroxyethylcellulose, locust bean gum, carrageenan gum,and xanthan gum.
 16. The composition of claim 1 wherein the hydratablepolymer is hydroxyethylcellulose.
 17. The composition of claim 1 whereinthe organophilic clay is an alkyl quaternary ammonium bentonite.
 18. Thecomposition of claim 1 wherein the water-swellable clay is selected fromthe group consisting of montmorillonite, attapulgite, Fuller's earth,and bentonite.
 19. The composition of claim 1 wherein thewater-swellable clay is bentonite.
 20. The composition of claim 1further comprising an effective amount of a dispersing agent.
 21. Thecomposition of claim 20 wherein the dispersing agent is lecithin.
 22. Acomposition for temporarily sealing a subterranean zone to prevent theuncontrolled flow of fluids into or from the zone comprising: a firstcomponent comprising oil present in an amount in the range of from about32% to about 62% by weight of the composition, wherein the balance ofthe composition comprises: a second component present in an amount inthe range of from about 10% to about 90% by weight of the balance of thecomposition comprising a hydratable polymer present in an amount in therange of from about 4.4% to about 14.6% by weight of the secondcomponent, an organophilic clay present in an amount in the range offrom about 0.4% to about 1.6% by weight of the second component, and awater-swellable clay present in an amount in the range of from about 84%to about 95% by weight of the second component; and a third component ispresent in an amount in the range of from about 10% to about 90% byweight of the balance of the composition comprising an inorganicmaterial that is readily acid soluble but substantially insoluble inneutral or basic water.
 23. The composition of claim 22 wherein thethird component is no more than about 1% by weight soluble in de-ionizedwater when tested at a pH of about 7, a temperature of about 212° F.,and a pressure of about 1 atmosphere.
 24. The composition of claim 22wherein the third component is selected from the group consisting ofcalcium carbonate, magnesium carbonate, barium carbonate, and iron (II)carbonate.
 25. The composition of claim 22 wherein the third componentis calcium carbonate.
 26. The composition of claim 22 wherein the thirdcomponent has a mesh size of up to about
 40. 27. The composition ofclaim 22 wherein the third component has a mesh size of about
 200. 28.The composition of claim 22 wherein the second component is present inan amount in the range of from about 30% to about 70% by weight of thebalance of the composition, and wherein the third component is presentin an amount in the range of from about 30% to about 70% by weight ofthe balance of the composition.
 29. The composition of claim 22 whereinthe second component is present in an amount of about 50% by weight ofthe balance of the composition, and wherein the third component ispresent in an amount of about 50% by weight of the balance of thecomposition.
 30. The composition of claim 22 wherein the oil is selectedfrom the group consisting of diesel oil, mineral oils, kerosene,vegetable oils and synthetic oils, esters, and olefins.
 31. Thecomposition of claim 22 wherein the oil is diesel oil.
 32. Thecomposition of claim 22 wherein the hydratable polymer is selected fromthe group consisting of guar gum, hydroxypropylguar, carboxymethylguar,hydroxyethylcellulose, carboxymethylcellulose,carboxymethylhydroxyethylcellulose, locust bean gum, carrageenan gum,and xanthan gum.
 33. The composition of claim 22 wherein the hydratablepolymer is hydroxyethylcellulose.
 34. The composition of claim 22wherein the organophilic clay is an alkyl quaternary ammonium bentonite.35. The composition of claim 22 wherein the water-swellable clay isselected from the group consisting of montmorillonite, attapulgite,Fuller's earth, and bentonite.
 36. The composition of claim 22 whereinthe water-swellable clay is bentonite.
 37. The composition of claim 22further comprising an effective amount of a dispersing agent.
 38. Thecomposition of claim 37 wherein the dispersing agent is lecithin.
 39. Acomposition for temporarily sealing a subterranean zone to prevent theuncontrolled flow of fluids into or from the zone comprising: a firstcomponent comprising oil present in an amount in the range of from about32% to about 62% by weight of the composition, wherein the balance ofthe composition comprises: a second component present in an amount inthe range of from about 10% to about 90% by weight of the balance of thecomposition comprising hydroxyethylcellulose present in an amount in therange of from about 4.4% to about 14.6% by weight of the secondcomponent, an alkyl quaternary ammonium bentonite clay present in anamount in the range of from about 0.4% to about 1.6% by weight of thesecond component, and water-swellable bentonite present in an amount inthe range of from about 84% to about 95% by weight of the secondcomponent; and a third component present in an amount in the range offrom about 10% to about 90% by weight of the balance of the compositioncomprising an inorganic material that is readily acid soluble butsubstantially insoluble in neutral or basic water.
 40. The compositionof claim 39 wherein the third component is no more than about 1% byweight soluble in de-ionized water when tested at a pH of about 7, atemperature of about 212° F., and a pressure of about 1 atmosphere. 41.The composition of claim 39 wherein the third component is selected fromthe group consisting of calcium carbonate, magnesium carbonate, bariumcarbonate, and iron (II) carbonate.
 42. The composition of claim 39wherein the third component is calcium carbonate.
 43. The composition ofclaim 39 wherein the third component has a mesh size of up to about 40.44. The composition of claim 39 wherein the third component has a meshsize of about
 200. 45. The composition of claim 39 wherein the secondcomponent is present in an amount in the range of from about 30% toabout 70% by weight of the balance of the composition, and wherein thethird component is present in an amount in the range of from about 30%to about 70% by weight of the balance of the composition.
 46. Thecomposition of claim 39 wherein the second component is present in anamount of about 50% by weight of the balance of the composition, andwherein the third component is present in an amount of about 50% byweight of the balance of the composition.
 47. The composition of claim39 wherein the diesel oil is present in an amount in the range of fromabout 43% to about 53% by weight of the composition.
 48. The compositionof claim 47 wherein the hydroxyethylcellulose is present in an amount inthe range of from about 6% to about 12% by weight of the secondcomponent.
 49. The composition of claim 48 wherein the alkyl quaternaryammonium bentonite clay is present in an amount in the range of fromabout 0.6% to about 1.3% by weight of the second component.
 50. Thecomposition of claim 49 wherein the water-swellable bentonite is presentin an amount in the range of about 90% by weight of the secondcomponent.